Fuel cells with high energy conversion efficiency have recently been developed actively for the purpose of suppression of global warming. Polymer electrolyte fuel cells (PEFCs) are being put into practical household or vehicle uses. PEFCs generate electricity using hydrogen and atmospheric oxygen as fuels, and the hydrogen is produced by steam reforming of hydrocarbon such as in city gas. Efficient steam reforming requires a catalyst, and there have been proposed catalysts such as Ru supported on alumina (Non-patent Publication 1), Pt, Ru, Rh, Pd, and the like supported on an oxide solid solution of Zr, Ce, and Fe or Y (Patent Publication 1), and Pt, Rh, Ni, Co, and the like supported on an oxide containing Ce, Pr, and the like (Patent Publication 2).
These catalysts contain a large amount of precious metals, which adds to cost and uncertainty of supply. Oxidation of the catalysts significantly deteriorates the rate of reforming hydrocarbon to hydrogen, which complicates setting of handling and operating conditions.
High cost of Pt catalyst, which is used in both anode and cathode, obstructs popularization of PEFCs. Particularly a large amount of Pt catalyst is used in the oxygen reduction 1/2O2+2H++2e−→H2O at cathode. In this regard, development of catalyst materials which can substitute or reduce the amount of Pt catalysts is being made actively.
As a catalyst for purifying exhaust gases used in vehicles or the like, so-called three-way catalyst is used, which oxidizes carbon monoxide and hydrocarbon in exhaust gases to carbon dioxide gas and water, while reduces nitrogen oxide to nitrogen and water. The three-way catalyst is composed, for example, of a catalytic metal, Pt, Rh, or Pd, and a co-catalyst, such as Ce, for improving the catalytic action of the catalytic metal, both supported on a catalyst support, such as alumina or cordierite. The precious metals used as such a catalytic metal have problems in cost and supply, as mentioned above.